Commutator-motor.



B. F- W. ALEXANDERSON.

COMMUTATOR MOTOR.

APPLICATION FILED JUNE 1, 1908.

Patented Feb. 22, 1910.

2 SHEETS-SHEET l.

UNITED %TATE PATENT @FFIDE.

ERNST F. W. ALEXANDERSON, 0F SCHENECTADY, NEW YORK, ASSIGNOR T0 GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

GOMMUTATOR-MOTOR.

Specification of Letters Patent.

Application filed .Tune 1, 1908.

Patented Feb. 22, 1910.

Serial No. 435,859.

'to motors intended for operation on both direct and alternatingcurrent.

In a prior application, filed January 12, 1907, Ser. No. 351,957, Ipointed out that a commutating field is more necessary in analternating-current motor than in a directcurrent motor, that analternating-current motor should not have so strong a main field as adirect-current motor, and that by taking advantage of these two facts,it is possible to adapt a motor for most satisfactory operation on bothdirect and alternating-current by using a portion of the stator windingto produce a commutating field for alternatingcurrent operation and toassist the main field winding for direct-current operation. In my formerapplication, I disclosed a system of connections, for obtaining thisdouble function of a portion of the stator coils, in which certain ofthe stator coils have their connections reversed with respect to theother stator coils in changing from direct to alternating-current, andvice versa.

My present invention, in one aspect, consists in a simplification of'theconnections and control of my former application.

In this aspect, my invention consists in connecting a portion of thestator winding in a local closed circuit so arranged that the currentsinduced therein in alternating-current operation produce a commutatingfield, and including this portion in the main motor circuit fordirect-current operation so that the current flowing through it assistsin producing the main field and excluding it for alternating-currentoperation. The connections in the local closed circuit may be madepermanent, so that the only change in connections necessary in shiftingfrom direct to alternating current, or vice versa, is to shift theconnections from the source of current from one motor lead to another.Thus, the connections of the motor and control system are greatly.simplified.

In another aspect, my invention consists of a novel arrangement of thestator windings, whereby the stator may be wound with uniform coils, anda portion of these coils may be so connected as to produce the desiredcommutating field.

My invention will best be understood by reference to the accompanyingdrawings, in which Figure 1 is a diagram of connect-ions of a motorarranged in accordance with my invention, and Fig. 2 showsdiagrammatically the construction and winding arrangement of the motor.

In Fig. 1, A represents the armature of a series-connected motor of thecommutating type adapted for operation on both direct andalternatingcurrent. The stator winding is divided into five groups ofcoils, B, C, D, E and F. The coils B act as the inducing or compensatingwinding for neutralizing armature reaction. I have indicated twelve ofthese coils connected in parallel groups of six coils each. C representsthe coils which, on alternating-current, act as the eX- citing ormagnetizing winding. I have indicated four of these coils connected ingroups of two each. D represents another group of coils which, ondirect-current operation, assist the coils C in producing the fieldmagnetization of the motor. 011 alternating-current operation all butone of these four coils are out of circuit and idle. The left hand coilis, however, connected in a local closed circuit formed by one coil Dand two coils E in parallel with two coils F and a resistance G. Thesecoils form a local circuit so arranged, as will hereinafter beexplained, that the current induced therein produces a suitablecommutating field. For forming this local circuit, the motor is providedwith three leads or connections (Z, c and f. The lead 6 is extended tothe transfer switch H, which is thrown from one position to the other,in changing from direct to alte-rnating-current operation. In additionto the lead 6, the motor leads Z) and c are also carried to the transferswitch. For alternating-current operation, the leads Z) and 0 areconnected to the source of current, so that the main motor circuitincludes the armature A, compensating winding B and the exciting ormagnetizing winding C, the local closedcircuit formed by coils E, F andone coil D serving only to produce a commutating field. Fordirect-current operi season rent tlowin in the local closed circuitthrough cons r1 opposing magneto-motive forces in th coils, so that ifthe lluxes of th se two so of coils were could produce will be shown,

no connnutating field. ii... however, these two sets of coils aredisplaced from each other, the space created by the displacement betweenthe sides of these C(Jll25 being opposite the points at whichcomnmtation takes place in the 170- At these points, therefore, when ontor. alternating current operation current flows" through these coilsthe e are leakage lields i which constitute the commutating lieldsdesired. It the one coil D, which is included in this motor-circuit,which forces through the coils l commutating field. The resistance Gserves to control the phase of the current, and, consequently, of thecommutating field.

As i have already said, the switch. ll is a transfer switch, which isthrown from one position to the other in passing from direct toalternatiiig-current. The switch is shown diagrammatically, and with itscontacts de eloped on a plane surface. For alternating-currcntvoperation, the switch is thrown to more the left hand contacts intoengagement with the contact lingers, which connects the leads 6 and c tothe secondary of a transformer I of variable ratio, and connects theprimary of this transformer to the source of cu rrcnt, as indicated bytile connection of the transformer to the trolley or current collectorJ. For direet-current opera tion, the switch H is thrown to its otherposition, thereby connecting lead 6 to ground and lead 0 to trolley Jthrough the resist-- ance K.

The winding arrangement of the motor will best be understood byreference to Fig. 2. In this tigure the coils and leads are lettered. tocorrespond with Fig. 1. Tue stator of the motor is constructed like thatof a standard induction motor, with its magnetic material uniformlydistributed. Jr four pole motor is shown, with twenty-four stator slots.The armature A is wound with a fractional pitch winding, as is indicatedby the span of the armature coils a as compared with the stator coils,which are all of uni form and full pitch. The purpose of the This meansand F in series produces perfectly interlinked they a and ll the currentproducing this i Ifractional pitch armature winding is, as has beenexplained in prior applications of mine, to obtain similar distributionsof stator and rotor magneto-motive forces for alte hating-currentoperation and the result ing advantages of improved commutation andincreased power-factor.

If the top slot in Fig. 2 be slot Bio. 1, and the slots are clockwisedirection, it will be considered as counted in a seen that thecon'ipensating or inducing winding B tills twelve of the twenty-fourslots. as follows: lots Bet, l, 2, (3, T. S. 152, 13, ll, l8, l1) and20. ther words. it fills erery other group of slots iach. Furthermore,it will be seen that the lines of magnetization of this .nding make anangle of 5 with the This is in line with the magneto- 3 horizontal. 7

1 motive force of the rotor. To bring this out clearly, the commutatorleads are so shown that the brushes in. are placed on the coznmu tatorlit opposite the ends of the armature conductors with which at anyinstant they re in direct connection, as they would be in a (lramme-ringarmature. 'lhe coils t], which form the exciting or magnetizing windingfor alternating-current operation, 5 occupy four slots which are thecentral slots, oi the groups of three slots each, unoccupied by thecompensating winding B. Lt will he seen that the lines of magnetizationof this winding are horizontal and vertical and, therefore, displacedninety electrical degrees from the lines of magnetization of the com- Ipensating and rotor windings. in the slots 3 on each side of the coil Care placed the coils l), E and i which, in dircct-cin'rent operation, a'e so connected as to a. the coil C in producmg the magnetizatum ot themotor. For altcrnatirig-current operation all but one of the oils l) areout of circuit and idle. ()ne of these coils is connected in series withthe coils id and l in local closed circuit. This coil. l), therefore,serves to drive through the coils E and ll :1 current for producing thecommutation held. The coils i) are in inductive relation to the coils(l, 2 and the voltr 'e induced in eacn coil l) in alternating-currcntoperation is consequently iubstantially in phase with the Voltage iacross tl e terminals of the coils C,-that i the terminals of theexciting winding. 'llhis :g being highly inductive, its ttu'minal YO] gois displaced nearly from the line voltage or, in other words, thevoltage at the motor terminals; and since the local closed circuit ismade suljistantially nein inductive the high resistance (t, the Ctlt'brushes in commutation.

but these coils are displaced from each other by two slots which lieopposite the points at which commutation is taking place in the rotor.Because of this displacement leakage fields are produced at thesepoints, and these fields being in phase with the current in the localclosed circuit which produces them are displaced approximately 90 fromthe phase of the voltage of the motor terminals. T his, as is nowwell-understood in the art, is the proper phase for a commutating fieldfor opposing the electroinotive force induced by the transformer actionof the exciting winding in the rotor coils short-circuited by the itwill be seen that the pitch of the armature coils is less than unity byan amount corresponding approximately to the portion of the statorperiphery occupied by the exciting or magnetizing coils C. The pointswhere commutation takes place in the rotor are thus brought beneath theleakage fields produced by the relatively displaced coils E and F.

The coilsin Fig. 2 are connected as is shown in Fig. l, and arrow headsare employed to assist in tracing the circuits. F or direct-currentoperation the current may be considered as entering at c. It then passesthrough the two coils E E in series, and one coil 1), to the point (Z. Asecond circuit from the source to this point exists through resistance G(see Fig. 1) and through lead f and the two coils I The current in coilsF is small, but assists the current in coils E in producing theirmagnetization. From point (Z, the circuit continues through the threeother coils to a point in direct connection with lead. 0. At this pointthe circuit divides into parallel paths, each path including two coilsC. The paths then join and the circuit passes through the lowercommutator brush 7%, armature A, and out through upper brush m. Thecircuit then again divides into parallel paths, each path including sixcoils B in series. "he two paths join at a point connected directly tothe lead Z). For alternating-current operation the current may beconsidered as entering at the lead 0 and passing through windings G,armature A, and winding B, and out at lead 6. At the same time aninduced current flows in the local closed circuit as has already beenexplained.

I do not desire to limit myself to the part-icular construction andarrangement of parts here shown, but aim in the appended claims to coverall modifications which are within the scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,

1. A motor of the commutator type, adapted for operation on both directand alternating-current, having a portion of its stator windingconnected to another portion of said winding and forming with said otherportion and the connections between them a local closed circuit, andconnections for including said portions in the main motor circuit fordirect-current operation and ex eluding them therefrom foralternating-current operation.

2. A motor of the commutator type, ad aptcd for operation on both directand alternating-current, having a portion of its stator windingconnected in a local closed circuit, phase-controlling means in saidlocal circuit, and connections for including said portion in the mainmotor circuit for direct-current operation and excluding it therefromfor alternating current operation.

3. A motor of the commutator type, adapted for operation on both directand alternating-current, having certain of its stator coils connected inparallel with other stator coils so as to form a local closed circuit,and connections for including said coils in the main motor circuit fordirect-current operation and excluding them therefron'i foralternating-current operation.

t. A motor of the commutator type, adapted for operation on both directand altermiting-current, having certain of its stator coils connected inparallel with other stator coils so as to form a local closed circuit,an impedance in series with one of the sets of coils which are inparallel with each other, and connections for including said coils inthe main motor circuit for direct-current operation and excluding themtherefrom for a1ternating-current operation.

A motor of the connnutator type, adapted for operation on both directand alternating current, having certain of its stator coils connected toother stator coils to form a local closed circuit, said coils havinginduced in them by the motor flux in alternatins current opention acurrent approximately 90 degrees out of phase with the terminalvoltageof the motor and being located to produce a commutating field oppositethe points where commutation occurs in the rotor, and connections forincluding said coils in the main motor circuit for direct currentoperation only.

6. A motor of the commutator type, adapted for operation on both directand alternating-current, having a set of its stator coils connected inparallel with a second set of stator coils displaced from the first set,the spaces created by the displacement be tween the sides of the coilsof the two sets being opposite the points where commu tation occurs inthe rotor and the local circuit formed by said" two sets of coils havinginduced in it by the motor flux in alternating-current operation acurrent approximately 90 out of phase with the terminal voltage of themotor, and connections for including said coils in the main motorcircuit for operation on direct-current only.

7. A motor of the commutator type having a stator with its magneticmaterial uniformly distributed and wound with unifor n coils, certain ofsaid stator coils being connected to form a compensating winding,certain others of said coils being connected to form an exciting ormagnetizing winding, certain other coils being connected to form a localclosed circuit producing a coimnutating field by the current induced insaid local circuit when the motor operating on alternating current, anda rotor haying coils of a fractional pitch less than unity by an amountcorresponding to the portion of the stator periphery occupied by thecoils forming the exciting or magnetizing winding.

8. A motor of the commutator type having certain of its stator coilsconnected to form a compensating winding, certain others of its statorcoils connected to form an exciting or magnetizing winding, and certainothers of its stator coils connected in paral lel with a second set ofstator coils displaced from the first set and forming there with a localclosed circuit, the spaces created by the displacement between the sidesof the coils of the two sets being opposite the points where theconnnutation takes place in the rotor, and the local circuit formed bysaid two sets of coils haying induced in it by the motor flux inalternating-current operation a current approximately 90 out of phasewith the terminal Voltage of the motor.

9. A. motor of the commutator type having a rotor wound with coils of afractional pitch, and having a stator with its magnetic materialuniformly distributed and wound with uniform coils, portion of saidstator coils being connected to form an inducing or compensatingwinding, another portion to form an exciting or magnetizing winding, andanother portion comprising coils the sides of which lie adjacent to thepoints where commutation takes place in the rotor and which areconnected in a local closed circuit adapted to produce a commutatingfield by the current induced in said local circuit when the motor is operated on alternating-current.

10. A motor of the commutator type having a rotor wound with coils of afractional pitch, and having a stator with its magnetic materialuniformly distributed and wound with uniform coils, a portion of saidstator coils being connected to form an inducing or compensatingwinding, another portion to form an exciting or magnetizing winding, andanother portion comprising two sets of coils connected in parallel witheach other so as to form a local closed circuit, said two sets beingsomewhat displaced from each other, the spaces created by thedisplacement between the sides of the coils of the two sets beingopposite the points where commutation occurs in the rotor.

11. A motor of the commutator type having a rotor wound with coils of afractional pitch, and having a stator with its magnetic material.uniformly distributed and wound with uniform coils, a portion of saidstator coils being connected to form an inducing or compensatingwinding, another portion to form an exciting or magnetizing winding, andanother portion com1'n'ising two sets of coils connected in parallelwith each other so as to form a local closed circuit, said two setsbeing somewhat displaced from each other, the spaces created by the displacement between the sides of the coils of the two sets being oppositethe points where commutation occurs in the rotor, and phase controllingmeans included in said local closed circuit.

In testimony whereof, I hate hereunto set my hand this 29th day of stay,1908.

ll tNSl F. W. ALEXANDERSON.

lVitnesses BENJAMIN B. HULL, HELEN Onrono.

